Methods of remote activation of a function present in an automotive vehicle are known. These methods are known under the phrase method of accessing the vehicle and/or starting the vehicle of the “hands-free” type. In such methods, the person entitled to perform the activation, frequently the driver of the vehicle, possesses an electronic key or an electronic fob as activation means performing the unlocking or the locking of the openable panels and/or being able to allow the starting of the vehicle corresponding thereto with an activation module.
An exemplary system for activation by detecting a position of an activation means at a predetermined distance from a vehicle is illustrated in FIG. 1. Such a system is partially integrated into a vehicle 5 by an activation module 1 communicating remotely with an activation means 4 exhibiting in this example the form of a fob for “hands-free” access to the vehicle 5.
The activation system comprises at least one omnidirectional antenna 6 mounted on the vehicle 5 and not only at the rear part of the vehicle. This antenna 6 is coupled to said activation module 1 and configured, on the one hand, to emit, preferably periodically, a frame of electromagnetic waves Te inducing an electromagnetic field in an electromagnetic emission space 10 around the vehicle 5 and, on the other hand, to receive electromagnetic waves in response Tr from the activation means 4.
When an activation means 4 associated with the vehicle 5 enters said emission space and receives at least one of the frames of electromagnetic waves emitted by the antenna 6, it can determine, for example with the aid of an identification code of the vehicle 5, that it is in the space of emission of an antenna 6 or of the antennas coupled to an activation module 1 with which it is remotely associated.
For a passive access and engine startup system, a method of attack called attack relay has been developed by criminals who are not authorized to perform the activation of a function present in the vehicle. In order for example to perform a startup, such a method of attack allows the activation module to be made to believe that said at least one activation means is located inside the vehicle whilst the apparatus simulating said at least one activation means and the criminal manipulating it are outside the vehicle.
FIG. 2 gives an example of attack relay. The criminal positions an attack relay with a reception module 2 in the or one of the detection zones around the automotive vehicle, whilst said at least one activation means 4 is not situated in this zone or one of these zones and an emission module 2a out of range of emission of the activation module 1. The attack relay 2, 2a receives a frame of electromagnetic waves emitted Te by the activation module 1 of the vehicle 5. This attack relay 2, 2a retransmits to said at least one activation means 4 this frame of electromagnetic waves emitted Te in the form of a retransmitted electromagnetic frame of waves Tt.
This transmission is effected with a very powerful signal, advantageously a divergent beam of powerful signals, it being given that the criminal does not know exactly where the activation means 4 is situated, for example in a residence 7 which the owner of the automotive vehicle 5 has entered.
Said at least one activation means 4 receives the retransmitted electromagnetic frame of waves Tt as if it were emitted directly by the activation module 1. In return, said at least one activation means 4 dispatches a response frame of electromagnetic waves Tr to the activation module 1 for the activation of the function present in the automotive vehicle. Indeed, if the activation module 1 were not able to correspond in emission with said at least one activation means 4 then outside of the emission zone, said at least one activation means 4 is on the other hand able to effectively re-emit toward the activation module 1, the type of electromagnetic response waves re-emitted by said at least one activation means 4 being of longer range, being for example radiofrequency waves, than the electromagnetic waves emitted by the activation module 1, for example low-frequency waves.
To defend against an attack relay, several solutions have been proposed. The first solution envisages that said at least one mobile activation means belonging to the person entitled to activate the function in the automotive vehicle be furnished with a motion sensor. When it is noted that said at least one activation means has not been moved for a predetermined duration, said at least one activation mean deactivates automatically. This solution is relatively expensive and exhibits the disadvantage of not being able to be fitted on already existing activation means.
It has also been proposed to keep an activation means stowed away in a shielded casing, when a user of the activation means knows that he will no longer be going to use his activation means for some unspecified period of time. The shielding allows said at least one means of activation to no longer receive any frame of electromagnetic waves emitted by the activation module, notably a frame of electromagnetic waves retransmitted by an attack relay. This solution has the disadvantage for the user of being very constraining by requiring him to stow away and to take out his activation means according to circumstances.
In addition, these solutions currently implemented against an attack relay do not make it possible to guarantee 50% protection against criminal activation.